LA-ICP-MS sphalerite and galena trace element chemistry and mineralization-style fingerprinting for carbonate-hosted Pb-Zn deposits: Perspective from early Devonian Huodehong deposit in Yunnan, South China

Abstract

The Sichuan-Yunnan-Guizhou metallogenic province (SYGMP) in the southwestern margin of the Yangtze block is an important Pb-Zn province in China. In the SYGMP, over 400 Pb-Zn deposits are mostly hosted in the Sinian, Lower Cambrian and Carboniferous sedimentary rocks and rarely in the Devonian carbonate rocks (e.g., Houdehong). For Houdehong, however, its ore-forming conditions and deposit type remain unclear due to limited geological and geochemical data available. In this study, LA-ICP-MS spot analysis and mapping were conducted to determine the trace element features in the sphalerite and galena from Huodehong. The results show that the sphalerite is characterized by enrichments in Ge and Tl but depletions of Fe, Mn, and Co. Most of these elements have widely varying concentrations and occur as solid solutions in the sphalerite crystal lattice. The critical element of Ge enters sphalerite through coupling substitution with Mn2+ for Zn2+ and/or Cd2+. The results calculated by empirical formula show that the sphalerite mineralization occurred under low-temperature conditions (<180℃). Meanwhile, the Houdehong galena contains low Se, Cd, Tl and Bi, and very low Ag (<1.0 ppm) and Sb (<5.0 ppm) concentrations, which is likely controlled by the original ore-fluid compositions. Trace element compositions of the Houdehong sulfides are generally similar to that of the sulfides from Mississippi Valley-type (MVT) deposits and many other Pb-Zn deposits in the SYGMP, but markedly different from those of volcanogenic massive sulfide (VMS), sedimentary exhalative (SEDEX) and skarn Pb-Zn deposits. Considering also the deposit geological and geochemical features, we considered that the Huodehong Pb-Zn deposit is of MVT. Our findings provide further geological and geochemical evidence for understanding the Devonian carbonate-hosted Pb-Zn mineralization in the region.